At the auction in a marine products wholesale market, for example in a fish market where fishes are landed from fisher boats, the landed fishes are sorted, cleaned, and arranged directly on the floor of the auction market in a heap of about 40 cm square separately according to fisher boats landed the fishes and to the kind of fish to prepare for auction. Auction site extends to about 300 m long, considerable time is needed until the last auction finishes, and there have been problems of drying and rising in temperature of fishes caused by being exposed to wind and sunlight.
In a whole sale market, collection, sorting, storing, trading, transportation, and disposal of fresh marine products are done in a short time, during which nearly all or all of the fresh marine products are exposed to outside air and transferred from owners to buyers. During that time period, the fresh marine products are exposed to an atmosphere contaminated with exhaust gases, bacteria, etc. It is desired particularly in the case of trading fresh marine products that trading is done in a state the fresh marine products are accommodated in a low temperature zone separated from said contaminated atmosphere. That is, a low temperature storage facility is required in a whole sale market for the purpose of hygiene and maintaining freshness of the products.
As to such a low temperature zone forming system as mentioned above, there have not been disclosed much proposals directly applicable to such situation. A proposal relating to a refrigerating apparatus in which a cold air curtain is formed across the opening of the apparatus was disclosed, for example, in Japanese Laid-Open Utility Model Application No. 01-28778.
The proposal relates to a refrigerating apparatus in which an air curtain is formed across the opening through which commodities are gotten in and out of the apparatus.
The apparatus is composed as shown in FIG. 9. A show case body 51 has a storage room 52 for accommodating commodities and an opening 53 is provided for getting the commodities in and out of the storage room. On both sides of the opening 53 are formed an air admission port 55 for sucking in cold airflow 54 and an air outlet port 56 to blowing out cold airflow 54, both the ports opposing to each other.
In the passage 57 under the bottom of the storage room 52 communicating the air admission port 55 with the air outlet port 56 are located a blower 58 for forcing circulation air, an evaporator 60 for cooling the circulation air in an ordinary operation, and a heat exchanger 59 for cooling the circulation air when defrosting the evaporator. In a base frame 61 are located a condenser 62 and compressor 63 of a refrigerating machine.
In an ordinary operation, refrigerant circulates from the compressor 63 through the condenser 62, heat exchanger 59, expansion valve not shown in the drawing, and evaporator 60 where the circulation air is cooled by the evaporation of the refrigerant, to be returned to the compressor 63. The high-pressure, high-temperature refrigerant gas compressed in the compressor 63 is cooled in the condenser 62 to be condensed to a liquid state, the liquid refrigerant is supercooled in the heat exchanger 59 and then expanded through the expansion valve to be evaporated in the evaporator 60 to cool the circulation air.
When defrosting the evaporator, the refrigerant is circulated from the compressor 63 through the condenser 62, evaporator 60, and heat exchanger 59 to be returned to the compressor 63. The evaporator 60 is defrosted by the sensible heat of the liquid refrigerant from the condenser 62. The liquid refrigerant supercooled through the defrosting process flows by way of an expansion valve not shown in the drawing to the heat exchanger 59 where it evaporates and cools the circulation air.
According to the proposal, as defrosting operation is possible by inverting the direction of the refrigerant circulation in an ordinary operation and the defrosting operation is done while the cooling circulation air is done, the rise in temperature in the storage room during defrosting is prevented. As an air curtain is formed across the opening of the storage room, the apparatus can maintain freshness of fresh marine products accommodated in the storage room.
Besides said proposal, a proposal relating to belt conveyer equipment for transferring cold food used to transfer and dispose foodstuffs and food articles in food processing factories such as meat, marine products processing factories, etc. was disclosed recently, for example, in Japanese Laid-Open Patent Application No. 11-287545. The equipment is composed as shown in FIG. 10. Cold air blow out openings 74a and admission openings 74b opposing to each other across the belt conveyer 72 are provided on both left and right sides along the transfer direction S of a belt conveyer 72 for transferring cold food, and cold space R is produced on the belt by the cold air.
A cooling section 75 is provided in the space between the upper, transfer side belt 72a and lower, return side belt 72b of the belt conveyer 72. Cold air cooled in the cooling section is sent to the cold air blow out openings 74a to be blown out onto the surface of the transfer side belt 72a and sucked from the admission openings 74b, thus the cold air is circulated.
With the composition mentioned above, cold space R is produced on the surface of the transfer side belt 72a and at the same time the rear side thereof is also cooled.
The above proposal can be applied to a low temperature zone forming system required not only in a food processing factory such as a meat, marine products processing factory but also for transferring and temporally storing foodstuffs in a wholesale market of marine products or fruits and vegetables.
As to a low temperature forming system in which an atmosphere of low temperature shielded from an outside contaminated atmosphere is formed, there has been no proposal directly applicable to the situation concerned. Proposals of heat storage tank in which heat is stored in a thermally stratified state have been disclosed hitherto. An example of such a proposal uses a thermal stratification type heat storage tank in which the difference in density of water depending on the temperatures thereof is utilized to store water in a stratified state without allowing hot water lower in density to mix with cold water high in density.
Besides said proposal, an apparatus and method for displaying and storing hauled fishes was disclosed in Japanese Laid-Open Patent Publication No. 2000-14315, in which hygiene and quality problems induced by the auction of hauled fishes arranged on the floor of the market was solved and hygienic storage of hauled fishes was made possible.
The display and storage apparatus is composed, as shown in FIG. 11, of a cooling part which is a cooling panel 78a with a brine passage 78b formed inside thereof and an insulation part 79 attached to the bottom thereof, hauled fishes being possible to be displayed on the surface of the cooling panel. Brine usable for food is supplied to the brine passage to cool the cooling panel. The apparatus is provided in a fish market and the distribution process is carried out on the display and storage apparatus.
As can be seen in the proposals mentioned above, it is required in a market that, a space formed into a box shape which can be moved as necessary is provided as a commodity storage facility, and the outside air including warm air in the space is driven out and instead cold air is supplied into the space to speedily replace the atmosphere inside the space by an cold atmosphere of uniform temperature distribution.
As a method of the displacement, there has been known a method of forming a fresh air zone in the lower part of a room near the floor where people reside or work by utilizing the thermal stratification of air caused by the temperature difference between the temperature of the air-conditioned air supplied to the room and that of the warm air heated by the heat generated in the room. As such was disclosed in Japanese Laid-Open Patent Application No. 06-185780 a method and apparatus for ventilation. According to the proposal, as shown in FIG. 12, air-conditioned air 82 lower in temperature than the temperature of the air inside the room 80 is blown out at low speed from a ventilation air outlet 81 located near the floor of the room 80, and nozzles are located near the ceiling for producing high speed air jet streams 83 to allow the air in the room near the ceiling to be ejected accompanied with the air jet streams through an exhaust opening located near the ceiling. Thus, ventilation can be performed efficiently.
However, with the prior art disclosed in said Japanese Laid-Open Utility Model Application No. 01-28778, there is a problem that the surfaces of the commodities dry out, for cold air for forming the air curtain strikes the accommodated commodities such as marine products.
Further, there is also a problem that cleaning is vexatious and accompanies difficulty because the air admission port, air outlet port, fan, etc. are located in the rear side of the cold storage room for accommodating marine products as commodities.
Further, the proposal is related to the utilization of an air curtain of cold air for shielding the cold storage room from outside atmosphere and there is no description about maintaining the storage room in low temperature.
Further, as the apparatus includes a cold air circulation mechanism (a heat exchanger, fan, air admission port, and air outlet port), the space for displaying commodities is limited and there is a problem that it accompanies difficulty to place the apparatuses to match the structure and availability of a market.
The prior art disclosed in said Japanese Laid-Open Patent Application No. 11-287545 is composed such that a cold space is formed on a belt conveyer for transferring processed cold food article by blowing cold air, and there is a problem similar to that which exists in said Japanese Laid-Open Utility Model Application No. 01-28778.
The prior art disclosed in said Japanese Laid-Open Patent Application No. 2000-14315 is related to low temperature storage using a cooling panel. The panel is used only for placing marine products such as hauled fishes thereon and there is no description about efficiently forming a low temperature zone around the hauled fishes placed on the panel.
The prior art disclosed in said Japanese Laid-Open Patent Application No. 06-185780 is related to the displacement of the air inside a room utilizing a well-known method of thermal stratification and not related to the formation of a low temperature zone for storing fresh foodstuffs such as marine products.
By the way, as mentioned before, low temperature storage facilities for the purpose of sanitation and maintaining freshness of foodstuffs are required in central whole sale markets handling mainly marine products, fruits and vegetables and prefabricated refrigerators or low temperature forming facilities are beginning to be provided there recently.
A displaying facility of hauled fishes capable of being removed easily, not a permanent facility, was proposed by the applicants of the present application and others.
Said proposal relates to a displaying and storing equipment to surround an auction market and fill the surrounded space with cold air.
The cooling system of the proposal for forming a cold zone is an open type, local cooling system in which the cold air is not recovered, and there is room for improvement. On the other hand, need for a low temperature storage facility is increasing and a low cost, compact, and highly efficient facility is desired.
Currently, the handling operation of fresh foodstuffs such as marine products from arrival to shipment in a market is done under ordinary temperature in many cases, and improvement from the viewpoint of hygiene and maintaining freshness is strongly demanded.
Presently, as to lowering the temperature in an auction market, there are attempts to include a whole auction market in a large box type facility, but in this case the reception of goods, prearrangement for auction, preliminary inspection, and shipment must be carried out under low temperature for a long time period and there arises a problem of maintenance of good health of workers working under a low temperature atmosphere.